Since the advent of printers, and specifically for low cost printers for personal computers, a variety of inkjet printing mechanisms have been developed and utilized in the industry. These inkjet printing mechanisms include the piezoelectric type, the electrostatic type and the thermal bubble type, etc. After the first thermal inkjet printer becomes commercially available in the early 1980's, there has been a great progress in the development of inkjet printing technology.
In an inkjet printer, a liquid droplet injector is one of the key mechanisms. To provide a high-quality and reliable inkjet printer, the availability of a liquid droplet injector capable of supplying high-quality droplets at high-frequency and high-spacial resolution is critical.
Presently, there are two types of inkjet printers that are available in the marketplace, the piezoelectric type and the thermal type. The thermal inkjet system, also known as thermal bubble inkjet system, as thermally driven bubble system or as bubble jet system utilizes bubble to eject ink droplets out of an ink supply chamber, while piezoelectric printers utilize piezoelectric actuators to pump ink out from a reservoir chamber. The principle of operation for a thermal bubble inkjet system is that an electrical current is first conducted to the heater by an electrode to boil liquid in an ink reservoir chamber. When the liquid is in a boiling state, bubble forms in the liquid and expands and thus functions as a pump to eject a fixed quantity of liquid from the reservoir chamber through an orifice and then forms into droplets. When the electrical current is turned-off, the bubble generated collapses and liquid refills the chamber by capillary force.
When evaluating the performance of a thermal bubble inkjet system, factors such as droplet ejection frequency, cross-talk between adjacent chambers and the generation of satellite droplets are considered. Two of these performance factors, i.e. the satellite droplets, which degrade the sharpness of the image produced and the cross-talk between adjacent chambers and flow channels which decreases the quality and reliability of the inkjet system are frequently encountered. In order to improve the performance of a thermal bubble inkjet system, these drawbacks must be corrected.
It is therefore an object of the present invention to a provide a micro droplet generator, particularly related to a thermal bubble inkjet head that does not have the drawbacks or the shortcomings of the conventional thermal bubble inkjet head.
It is another object of the present invention to provide a thermal bubble inkjet head that is equipped with symmetrical heaters of the off-shooter type for generating bubbles.
It is a further object of the present invention to provide a method for fabricating a thermal bubble inkjet head that utilizes rapid ink refill mechanism to generate ink droplets.
It is another further object of the present invention to provide a thermal bubble inkjet head that is equipped with a primary and an auxiliary ink chamber.
It is still another object of the present invention to provide a thermal bubble inkjet head that is equipped with two separate heaters as two sources for generating bubbles.
It is yet another object of the present invention to provide a method for fabricating a thermal bubble inkjet head that is equipped with symmetrical heaters and a rapid ink refill mechanism.
It is still another further object of the present invention to provide a method for fabricating a thermal bubble inkjet head that is equipped with symmetrical heaters and a rapid ink refill mechanism by utilizing two separate thick photoresist deposition processes and a nickel electroplating process.